Protein Synthesis: The Dance of Amino Acids
What happens after peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain?
Question 6 options:
A. moves to the P site of the ribosome
B. releases the growing polypeptide chain
C. forms a covalent bond with the P site of the ribosome
D. picks up another amino acid to add to the chain
E. forms a peptide bond with A site of the ribosome
Answer:
Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site moves to the P site of the ribosome.
During protein synthesis, the ribosome facilitates the formation of peptide bonds between amino acids to build a polypeptide chain.
1. Aminoacyl-tRNA binding:
The transfer RNA (tRNA) carrying the amino acid corresponding to the codon in the A site of the ribosome binds to the ribosome. This tRNA is referred to as the aminoacyl-tRNA.
2. Peptide bond formation:
The amino acid on the aminoacyl-tRNA in the A site forms a peptide bond with the growing polypeptide chain attached to the tRNA in the P site. This bond formation is catalyzed by the ribosome.
3. Translocation:
After peptide bond formation, the ribosome undergoes a process called translocation. During translocation, the tRNA in the A site, which has now contributed its amino acid to the growing chain, moves to the P site of the ribosome.
4. Empty A site:
The movement of the tRNA from the A site to the P site creates an empty A site on the ribosome, ready to receive the next aminoacyl-tRNA corresponding to the next codon in the mRNA sequence.
5. Continuation of translation:
With the A site now empty, the process of translation continues as the ribosome moves along the mRNA, bringing in new aminoacyl-tRNAs to add amino acids to the growing polypeptide chain.
In summary, following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site moves to the P site of the ribosome through the process of translocation. This movement prepares the ribosome for the addition of the next amino acid to the growing polypeptide chain during protein synthesis.